1. Field of the Invention
The present invention relates to a motion assist device for assisting a periodical motion of a creature by applying a force to the creature.
2. Description of the Related Art
There has been proposed a device for assisting a periodical walking motion of a creature, such as a human whose body part such as a lower limb or the like is suffering from physical hypofunction, by applying a periodically varying force to the creature (refer to Japanese Patent Laid-open No. 2004-073649). There has also been proposed a device for assisting or guiding a periodical motion of a human by adjusting strength of a force applied to the human according to a model (a spring model) representing a behavior feature of a virtual elastic element so as to match a motion scale of the human with a desired motion scale thereof (refer to Japanese Patent Laid-open No. 2007-061217).
According to the spring model, the strength of force applied to the human is adjusted according to a motion rhythm of the periodical motion of the human. Therefore, when an action of the human is performed fast to some extent, the periodical motion of the human can be assisted with a sufficient force from the viewpoint of matching the motion scale of the human to the desired motion scale thereof. However, on the other hand, when the human acts slowly due to remarkable physical hypofunction or the like, it is possible that the strength of force applied to the human by the motion guiding device becomes insufficient from the viewpoint of matching the motion scale of the human to the desired motion scale thereof.